Implement CSSOM Smooth Scroll API

Source/core/dom/Element.h

Index: Source/core/dom/Element.h
diff --git a/Source/core/dom/Element.h b/Source/core/dom/Element.h
index b7ab024e80db9358e02f6172f6c7f81534ecf041..f3fc021adeee3266fd6567358d976523a1266a5a 100644
--- a/Source/core/dom/Element.h
+++ b/Source/core/dom/Element.h
@@ -36,6 +36,7 @@
 #include "core/page/FocusDirection.h"
 #include "core/rendering/RegionOversetState.h"
 #include "platform/scroll/ScrollTypes.h"
+#include "platform/scroll/ScrollableArea.h"
 
 namespace WebCore {
 
@@ -185,9 +186,9 @@ public:
     int clientHeight();
     virtual int scrollLeft();
     virtual int scrollTop();
-    virtual void setScrollLeft(int);
+    virtual void setScrollLeft(int, ScrollBehavior = ScrollBehaviorAuto);
     virtual void setScrollLeft(const Dictionary& scrollOptionsHorizontal, ExceptionState&);
-    virtual void setScrollTop(int);
+    virtual void setScrollTop(int, ScrollBehavior = ScrollBehaviorAuto);
     virtual void setScrollTop(const Dictionary& scrollOptionsVertical, ExceptionState&);
     virtual int scrollWidth();
     virtual int scrollHeight();
@@ -571,6 +572,9 @@ protected:
 
     Node* insertAdjacent(const String& where, Node* newChild, ExceptionState&);
 
+    virtual void setScrollLeftInternal(int, ScrollBehavior);
+    virtual void setScrollTopInternal(int, ScrollBehavior);
+
 private:
     void styleAttributeChanged(const AtomicString& newStyleString, AttributeModificationReason);